1. Field of the Technology
The technology presented herein relates to an image processing apparatus and a storage medium storing an image processing program, and particularly to an image processing apparatus operated by using an input device having image pickup means and a storage medium storing an image processing program.
2. Description of the Background Art
There have been disclosed position detection systems, in which a light source of an infrared light is used as a marker whose image is taken, and the taken image is analyzed to obtain a position aimed at by a user. One of such systems is disclosed in, e.g., Japanese Laid-Open Patent Publication No. 11-305935 (hereinafter, referred to as a patent document 1).
The patent document 1 discloses a game as an embodiment of a position detection system in which a player uses, as a game controller, a gun having an image pickup device mounted thereon, and performs shooting. In the system, four light sources each emitting an infrared light are respectively fixed, on four corners of a display screen, as imaging targets of the image pickup device, and a position on the display screen pointed by the gun is detected based on positions of the imaging targets in an image taken by the image pickup device. Then, a virtual shooting game is executed by using the position pointed by the gun as a position aimed at by the player. As disclosed in the 21st paragraph of the patent document 1, in the case where the player is allowed to discretionarily change a distance between the image pickup device and a target (i.e., a distance between the image pickup device and the markers), the image pickup device is provided with a controllable zoom function, and the zoom function is controlled such that each of the markers in the taken image is always in an appropriate size, thereby detecting the aimed position precisely.
However, there has not been a technique in which a distance between an input device (game controller) and an imaging target is used for an input operation. For example, in the position detection system disclosed in the patent document 1, the distance between the image pickup device and the markers is used merely for adjustment. In fact, changes in such a distance are negative factors which interfere with precise operation inputs.